Heat exchange surface construction and device embodying the same



Sept. 25, 1951 G. w. MILLER ETAL 2,569,112

HEAT EXCHANGE SURFACE CONSTRUCTION AND DEVICE EMBODYING THE SAME Filed July 31, 1947 2 Sheets-Sheet l 6 E/citgiwjfells.

Sept. 25, 1951 G. w. MILLER HAL HEAT EXCHANGE SURFACE CONSTRUCTION AND DEVICE EMBODYING THE SAME 2 Sheets-Sheet 2 Filed July 31, 1947 6Z3 wm'zzer w .521 are? 00 0 0 I 1 r i y Patented Sept. 25, 1951 2 569 1 UNITED STATES PATENT OFFICE I near EXCHANGE SURFACE CONSTRUCTION AND DEVICE nmnonrmo THE SAME Glen W. Miller, Covina, and Edward Lucas Kells, Alhambra, Calif.

Application July 31, 1947, Serial No. team 18 Claims. (Cl. 237-67) l 2 The present invention relates to heat exchange In the drawings surfaces or systems and to particular apparatus Figure 1 is a perspective view of a deep fat embodiments incorporating the same. fryer embodying the invention;

More particularly, the invention provides new Figure 2 is a horizontal section and plan view and improved heat transfer surfaces, adapted to of the apparatus of Figure 1, taken on line 2-! increase the absorption of heat from a heat exof Fi r change medium and to improve the tran fer Figure 3 is a transverse vertical section on thereof to a body to be heated. line of Figure 2;

A primary object of the invention is to Figures 4 and 5 are fragmentary sectional and vide an extended heat exchange surface for the end elevatiohal views of modified heating surface increased absorptiori of heat from a source and structures showing the flexibility and adjust to provide simultaneously, improved conduit 3? system b t di in means for controlling the flow of a heated fluid. gum somew agmmma c A further object is to provide heat exchange '5 tive view and partial section, showing an hermefins which absorb heat from the source and which many sealed bfler mwhamsm loyed as a duct heater; also provide conduits for confining and directing p the flow of products of combustion or the like. Figure 7 is vertical sectional View and partial elevation, with parts broken away, showing the Another bject is to construct the fins that boiler and associated parts on an enlarged scale; the cross-sectional area and flow capacity of the Figure 8 is a bottom plan and inverted herb conduits may be readily varied, to eilect the most zontal section, taken on line M of Figure desirable heat transfer factor, consistent with Figures 9 and 10 are similar t Figures 4 and adequate flow of the heating medium- 5, showing the flexibility and adjustability of the A othe Object the invention 18 to provide heat exchange system when'applied to a curved embodiments in which the heat exchange surface 2 surface,

functions in new and improved ways with other The deep fryer shown in Figures 1-3 comprises pp t s feat o s t nt o vertical side walls II and i2 and vertical and in the embodiments shown in the accompanying w ll I: and I4, joined at their corners in any drawings and described below, provides," in one approved manner and terminating at their upper case, an improved cooking vessel, known in the edges in outwardly flaring drain surfaces It, I, art as a deep fat fryer, and in another, an im- I1, and II, respectively. The bottom comprises proved hermetically sealed boiler-condenser downwardly and inwardly inclined, sloping secassembly adapted for use as a duct heater or tions 20 and 2|, joined to the end and side walls the like. and terminating at their inner edges in a Another object, in connection with the flrst downwardly p cti o it i y extending of these embodiments is to provide improved trough or channel 22, defined by vertical side means for evenl heating the liquid frying mewalls 23, 2 and a, substantially horizontal, but dium, to prevent burning thereof or local overcentrally Smpmgwan the ends of heating. Another object is to improve the the channel-being closed by downward continuculation of the frying medium and to provide tions 26 of the end walls and a tn or m like 1m uflties ieces of food Within the interior of the vessel, there are a and f which becomepentmmed m plurality of relatively heavy, thick heat exchange the frying medunm iins or blocks 30, 3|, defined by inclined bottom sec: edges secured, as by welding, to the upper sur- A further object in connection with the ad faces of the, bottom sections in and 2|, vertical embodiment is pmvlde an improved boner outer edges similarly secured to the side walls structure, and an improved liquid and vapor cir- H and '2' horizontal top edges 32 and u, and

culating system between the boiler and the convertical inner edges 34 and 35. which may be dense aligned with the side walls 23 and N of the other oblects and advantagesfit the invention 0 longitudinal channel, trough, or trap 22.

will be apparent from a consideration of the The bottom wall 25 of t trough may be profollow description of the specific embodiments vided with a central, valved outlet or drain 3,

of the invention, shown for purposes of illustrat, t 1 point i t tt tion inthe accompanying drawings and described Upon the lower, outer surface of the inclined below: 05 bottom sections 2| and II there are secured a plurality of heat exchange fins of special design. In the embodiment illustrated, each fin (except the endones) comprises a portion 40 secured to and lying against the outer face of the bottom, another portion 4| projecting outwardly from the secured portion 40 and still another portion 42 turned laterally and projecting away from the second portion in the opposite directionfrom the first. The free edge 43 of the portion 42 is positioned adjacent to the next adjacent fin and cooperates with the outwardly projecting portion 4| thereof to provide a conduit 45 for the flow of a heat exchange medium as hereinafter explained.

Preferably, the inner portion or flange 40 of each fin is welded to the undersurface of the bottom section 20 or 2| and the outer edge 43 of the outer portion or flange 42 is welded to the line of junction or corner 46 between the outwardly projecting portion or flange 4| and the outer flange 42 of the next adjacent fin. If desired, each outer flange 42 may slightly lap the heel or corner 46 of the next adjacent one, but the butt joint shown in the drawing has been found satisfactory.

In the embodiment shown in Figure 2, each inner flange 40 is of the same length as the outer flange, but it is entirely feasible to make the inner flanges narrower, simply providing suflicient width to facilitate welding, as suggested at 40a in Figure 4.

At the ends, the fins may be constructed differently, as indicated at 50 and The former fin consists simply of an outwardly projecting flange, having its inner edge welded to the bottom wall of the vessel and to the inner flange 40 of the next adjacent fin, and an outer laterally turned fin 52, welded or otherwise secured to the corner 46. The fin 5|, at the opposite end, may consist simply of an L-shaped member having its inner leg 53 welded to the vessel bottom and its outer edge 54 welded to the shortened flange 42' of the next adjacent fin. Of course, any other suitable structure may be employed at the ends of the series of interconnected fins to finish the series and to provide a neat appearance.

It is apparent that the fins and the conduits formed thereby project upwardly along the undersurface of the inclined bottom sections 20 and be provided between the side walls of the trough 22,' to prevent overheating, and the vessel as a whole may be supported by rods 65, 66 having their outer ends secured to the burners and their inner ends to the side walls of the trough. Of course, any other suitable supporting means may be employed.

As indicated in broken lines at 61 and '68, collecting hoods for the products of combustion may extend along the side walls of the vessel, above the open upper ends of the conduits, to lead the gases to a flue or the like.

It will be noted that the outwardly projecting flanges 4| of the fins in Figure 2 are connected to their inner and outer flanges by angles of approximately 120, thereby providing conduits which, in cross-section are oblique parallelograms, having a cross-sectional area of predetermined amount, controlled by said angles, other factors being constant. In the form shown in Figure 4, however, the angles between inner flanges 40a, outwardly projecting flanges 4 la, and outer flanges 42a are with the result that the conduits are rectangular in cross-section and are of maximum area, the dimensions of the flanges Ho and 42a being the same as the corresponding flanges in Figure 2. Similarly, in Figure 5 the angles between flanges 40b, outwardly projecting flanges M1), and outer flanges 42b are considerably flatter than in Figure 2, being approximately thereby materially reducing the cross-sectional area of the conduits, the other dimensions remaining the same.

Hence, the present invention contemplates a simple means for correlating the heat exchange characteristics of the surface with the fiow capacity of the heat exchange medium. If the volume of flow of the products of combustion is relatively small, a construction as suggested in Figure 5 may be employed, thereby providing relatively great heat absorbing surface area with relatively small conduit area, to effect a most efilcient heat transfer rate, whereas if a higher gas fiow rate is desired, the conduit area relative to the fin surface area may be increased as suggested in Figure 4.

In the use of the form of the apparatus shown in Figures 1-3, the vessel is filled to a suitable level with cooking fat, such as hydrogenated vegetable oil, lard, or the like and heat is applied by the gas burner. The flames and the products of combustion rapidly raise the fins to an elevated temperature, whereby heat is transferred to the bottom of the vessel by conduction through the fins and by radiation from the inner surfaces of the outer "flanges to the inner flanges and directly to the vessel bottom, when relatively narrow flanges are employed in spaced apart relation. Heat is also conducted from the vessel bottom sections 20 and 2| to the relatively heavy baflies or fins 30 and 3|, disposed interiorly of the vessel. As a result, a circulation of the liquid fat in the vessel is set up along a plurality of circular paths between the several fins. upwardly along the bottoms 20 and 2| and along the sides II and I2, and downwardly along the longitudinal center line, above the trough 22. Hence, any particles of food or the like entrained in the fat are deposited in the trough out of the way. The fat in the trough is considerably cooler than elsewhere in the vessel, since it is not subjectedto the direct application of heat, and therefore has no tendency to rise. Hence, impurities remain indefinitely in the trough, until the vessel is cleaned.

The bafiles or fins 30 and 3| not only tend to produce the improved circulation referred to above, but result in an even heating of the vessel contents, thereby preventing burning and local overheating. Since they increase the heat exchange area interiorly of the vessel in contact with the fat, they facilitate raisin the liquid fat to cooking temperature in the minimum time, without burning or scorching. Moreover, the horizontal upper surfaces of the fins constitute an efficient means for supporting the foraminous receptacles in which the food to be fried is placed, for immersion in the fat and for removal therefrom, as is well understood in the practice of French frying.

The cooking apparatus of the present invention has improved heat exchange characteristics and is eflicient in use; yet it is far simpler and less expensive than conventional constructions which employ immersion heaters, making it necessary to pierce the side walls of the vessel. Moreover, the cleaning and maintenance of the apparatus is greatly simplified, since there are no internal obstructions, and burn-outs are practically eliminated by the novel conduit-forming fin structure.

The embodiment of the invention shown in Figures 6-10 is an hermetically sealed boiler-condenser mechanism arranged as an air duct heater, adapted to supply heat to residences and the like. Such heaters at the present time fall into two general classes. In one, direct flred heat exchangers are associated with the air ducts, and

'hot products of combustion are passed through sibility of bum-outs in the heat transfer surfaces.

which would result in carrying flame and high temperature gases through the ventilating system with the possibility of setting the building on fire.

The indirect duct heater, using water or steam as the medium to supply heat to the air flowing through .the duct has some advantages, but complications and difficulties are encountered in that auxiliary equipment necessarily employed, such as pumps, liquid level controllers, make-up systems, traps, air valves and the like.

In accordance with the present invention, air, other gases or liquids in ducts or pipes are heated by inserting in the duct a condenser connected to an external boiler. The boiler-condenser system thus formed is evacuated of all non-condensabl gases and is permanently. hermetically sealed. Hence, the system, at normal atmospheric temperatures and in the absence of the application of external heat is under a high vacuum and is fllled with a fluid such as water in the liquid phase and thereabove in the vapor phase. The system provides an extremely simple arrangement having all of the advantages of the indirect duct heater systems employing water or steam coils, yet none of the mechanical complexity thereof. It has the further advantage of always transferring heat to the gas or liquid within the duct or pipe at the lowest coil surface temperature possible for the quantity of heat to be transferred under the existing conditions.

The boiler may be enclosed within a casing II, with a layer of insulating material 1| interposed between the casing and the external boiler wall 12. In the preferred embodiment, the boiler is annular in form and consists of outer and inner walls 12 and II, spaced apart a suitable distance and arranged throughout the major portion of their vertical extent as concentric cylinders. Their upper and lower edges may be turned toward each other, with marginal portions I4, I! welded together, to provide an hermetically sealed internal space Ii.

The lower marginal portion ll of the annular boiler may be supported upon a flanged ring 11, welded to the outer casing II and having legs 18 associated therewith.

The exterior surface of the inner boiler wall 13 is provided with a plurality of conduit forming heat exchange fins ll, generally similar to the flns described above in connection with the first embodiment of the invention. Each consists of an inner portion ll having its surface juxtaposed against and preferably welded to the face of the boiler wall II, a second outwardly projecting portion 82 and a third portion It turned laterally and projecting "away from the second portion inthe opposite direction from the flrst. The free edge of each flange II is positionedadiacent to a portion of the next adjacent fln, preferably welded thereto, and cooperating therewith to provide a conduit 84 for the flow of a heat exchange medium. Thus, the flanges provide an annular series of conduits adjacent the external surface of the inner boiler wall. Products of combustion from a burner Ii are directed upwardly into these conduits by bame means consisting of a circlllal' miner-tome bottom plate It and an outwardly and upwardly sloping, frusto-conical plate extension l'l, ylhich may have its upper edge secured in any appropriate manner to the lower edges of, the nanges l3. 1

vAdJacent the upper edges of the fins. there is a hood l8, communicating with a flue I e'xtending through a central aperture in'aicover casing section It. Products of combustionfpassing upwardly through the conduits u fornied by the flns I! are collected within the hoofii and delivered to the flue. A conventional downdraft preventer ii, I! may be employed-{as is well understood in the art. The slightly flanged lower end 93 of the hood ll may be supported upon the upper edges of the vertical flns ll.

7 Within the interior 18 of the boiler is a body of vaporizable liquid .5, such as water, the normal level being indicated at Ll. In the operation of the boiler, during violent boiling of the liquid, the level may rise considerably, as v indicated at L2, the upper portion being in the form of a mixture of liquid and vapor bubbles. An outlet conduit it, connected and hermetically sealed to the margins of an opening in the" outer side wall I! of the boiler, above the normal water level, extends outwardly and is connected to the upper enlarged section II of a vertical riser indicated generally at I", the joint being hermetically sealed.

An inlet conduit "I, which preferably constitutes an integral, lateral extension of the lower reduced section III of the riser extends through the casing and insulation and is hermetically sealed to the margins of another opening in the outer side wall I! of the boiler, well below the liquid level therein.

The upper section it of the riser isiturned' laterally as at I (Figure 6) and constitutes a header for a plurality of condenser tubes I, shown diagrammatically in Figure 6 as "extend ing across a conduit section III, through which air or gas is adapted to flow, in heat exchange relation with the tubes. It should be understood that the condenser in the duct section ni ay take any conventional form and the showing in Figure 6 is purely diagrammatic.

The lower ends of the tubes I are in her- "metically sealed communication with the intethe liquid that a mixture of liquid and vapor would enter the upper riser section, preventing the return of condensate and the separation of liquid from the frothy mixture and the return of the separated liquid to the bottom of the boiler. In accordance with the present construction, however, any mixture of liquid and vapor entering the outlet conduit 98 and the vertical riser 99 will be separated therein and will drop directly down into the return leg I02, for delivery through conduit I 0| to the bottom of the boiler. This action is facilitated by natural convection, the liquid in the leg I02 being cooler and heavier, and by reason of the difference in the hydrostatic pressure in the boiler and leg I02 respectively, the former being a mixture of liquid and vapor and therefore being lighter.

It will be understood that the entire system is evacuated of air and non-condensable gases. Hence, any heat applied from the burner 85 to the-exterior surface of the inner wall of the annular boiler and to the heat exchange fins 80 will immediately cause the liquid to boil, thereby raising the pressure in the riser 99 and in the condenser. As heat is extracted from the condenser tubes and the vapor therein by air or gas flowing through the conduit section I05, the vapor condenses in the tubes and the-condensate returns through the header I06, downturned section I01, return leg I02 and inlet conduit section llll.

As indicated in Figure 6, the gas supply line Ill may include a manual cut-ofi valve Ill and a safety valve H2, adapted to be closed upon the occurrence of excessive heat or pressure conditions in the boiler, by any approved means. A variable valve I I! may be actuated and controlled in known manner by a thermostat positioned in the room to be heated or in the duct itself. Since such valves and their control means are known to the art, they are simply shown diagrammatically in Figure 6.

Figures 9 and 10, when compared with Figure 8,

show the manner in which the angles between the various flanges of the fins may be changed to vary the cross-sectional area of the conduits for the products of combustion, as compared to the fin surface area. The invention is not limited to the details of construction shown in the accompanying drawings and described above, but includes all modifications coming within the scope of the appended claims and their equivalents.

We claim:

1. In a heat exchanger, a heat transfer surface, a plurality of fins associated with theheat receiving face thereof, each fin comprising a portion having a surface secured directly to said face, another portion projecting outwardly from one edge of the secured portion, and still another portion turned laterally and projecting away from the remote edge of the second portion in the opposite direction from the first, the free edge of the last-mentioned portion being positioned adjacent to a portion of the next adjacent fin and cooperating therewith and with the said heat receiving face to provide a longitudinally unobstructed conduit for the flow of a heat exchange medium, and burner means below said fins for delivering a gaseous heat exchange medium to the lower ends of said conduits.

2. A heat exchange structure comprising a heat transfer surface, a plurality of similar, parallel fins associated therewith, each fin comprising an elongated, outwardly projecting, intermediate web, an elongated inner flange projecting laterally at a predetermined angle from the inner edge of the web and secured throughout its entire length and width to said surface, and an elongated outer flange projecting at a predetermined angle in the opposite direction from the outer edge of the web, the outer flange being coextensive in length with the web and being secured at its free edge to the next adjacent fin at the line of junction between the intermediate web and the outer flange thereof and providing a laterally closed, longitudinally unobstructed conduit for a heat exchange medium, the crosssectlonal areas of the conduits so formed being determined by the angles between the flanges and the web, other factors remaining constant, and burner means below said fins for delivering a gaseous heat exchange medium to the lower ends of said conduits.

3. A heat exchange structure in accordance with claim 2 characterized in that the inner flange is relatively narrow and that the inner flanges of the adjacent. fins are spaced apart, 4

leaving said heat transfer surface therebetween directly exposed to the heat transfer medium in said conduits.

4. A heat exchange structure in accordance with claim 2 characterized in that the outer flange is wider than the inner flange and is welded by a continuous, substantially hermetic joint to the adjacent fin.

5. A heat exchange structure in accordance with claim 2 characterized in that the outer flange is secured by a continuous weld to the adjacent fin at the outer corner thereof, at the line of junction of its web and outer flange.

6. A heat exchange structure in accordance with claim 2 characterized in that the inner and outer flanges are welded to the heat transfer surface and to the adjacent fin respectively.

7. A cooking vessel comprising downwardly and inwardly sloping lateral bottom sections and a longitudinally extending, central channel therebetween, and a plurality of outwardly projecting fins extending upwardly along and secured to the outer surfaces of said sections, and having laterally turned outer portions having their edges positioned adjacent to and cooperating with adjacent fins to provide heat absorbing conduits for the flow of a heat exchange medium therethrough.

8. A cooking vessel having downwardly and inwardly sloping bottom sections, a plurality of longitudinally spaced, transversely extending, vertically arranged heat transfer fins within said .vessel connected in heat exchange relation to said bottom sections, and a plurality of fins projecting from the other side of said bottom sections having laterally turned portions spaced therefrom and cooperating with adjacent fins to define heat absorbing conduits for the flow of a heat exchange medium therethrough.

9. A deep frying vessel having substantially vertical side walls, downwardly and inwardly sloping lateral bottom sections and a longitudinally extending central depressed channel at the inner ends of said sections, and a plurality of relatively thick longitudinally spaced, transversely extending vertically arranged heat transfer fins within said vessel supported upon said bottom sections, having their inner vertical edges aligned with the sides -of the central channel and having upper horizontal edges spaced below the upper edges of the side walls and adapted bottom sections, having their inner vertical edges aligned with the sides of the central channel and having upper horizontal edges spaced below the upper edges of the side walls and adapted to support a receptacle for eomestibles to be tried, a plurality of outwardly projecting fins extending upwardly along the outer surfaces of said sloping bottom sections, said fins having laterally turned outer portions cooperating with adjacent fins to provide heat absorbing conduits for the fiow of a heat exchange medium, and

means adjacent the lower ends of said conduits for delivering a heated medium thereto.

.11. A cooking vessel having downwardly and inwardly sloping bottom sections, a plurality of longitudinally spaced, transversely extending,

vertically arranged heat transfer fins within said vessel connected in heat exchange relation to said bottom sections, and a plurality of outwardly projecting fins extending upwardly along the outer surface of said inclined bottom sections, each fin comprising a portion having a surface secured to the adjacent bottom section, another portion projecting outwardly from the first por.-..

tion and a third portion turned laterally and projecting away from the second portion in the opposite direction from the first, the free edge of the third portion being positioned adjacent to the next adjacent fin and cooperating therewith to provide a conduit for the fiow of a heat exchange medium.

12. An hermetically sealed boiler comprising a section having a plurality of walls, including a substantially upright heat exchange wall, defining an hermetically sealed interior space, a body of vaporizable liquid sealed in said space in the absence of non-condensable gases, a plurality of upright fins projecting from the exterior surface of said upright wall, having laterally turned portions spaced therefrom and cooperating with adjacent fins to define heat absorbing conduits for the fiow of a heat exchange medium-and means adjacent the lower ends of said conduits for delivering such a medium thereto.

13. An hermetically sealed boiler-condenser assembly comprising a boiler having a plurality of walls, including an upright heat exchange wall, defining an hermetically sealed interior space, a body of vaporizable liquid in said space in the absence of non-condensable gases, a plurality of upright fins projecting from the exterior surface of said wall having laterally turned portions cooperating with adjacent fins to define heat absorbing conduits for the flow of a heat exchange medium, a condenser and a riser establishing hermetically sealed communication between the condenser and the boiler at points above and below the upper surface of said body of liquid, for the delivery of vapor to and the return of condensate from the condenser, and means adjacent the lower ends of said conduits for delivering a heat exchange medium thereto.

14. An hermetically sealed boiler-condenser assembly comprising a boiler having upright concentric cylindrical walls defining an annular hermetically sealed interior space, a body of vaporizable liquid partially filling said space in the absence of non-condensable gases, a plurality of upright fins projecting from the exterior surface of at least oneof said walls, said fins having laterally turned portions cooperating with adjacent fins to define heat absorbing conduits for the flow of a heat exchange medium therethrough, a condenser and hermetically sealed conduit means connecting the condenser to the interior space of the boiler at spaced points above and below the upper surface of said body of liquid for the fiow of vapor from and the return of condensate to the boiler, and means adjacent the lower ends of said conduits for delivering a heat exchange medium thereto.

15. A boiler comprising substantially concentric upright walls spaced apart through the major portions of their length and hermetically sealed at their upper and lower edges to provide an annular interior space for a body of liquid to be vaporized, a body of insulating material surrounding the outer surface of the outer wall, a plurality of substantially upright fins projecting from the exterior surface of the inner wall and all including laterally turned portions spaced from the last-mentioned wall and cooperating with the next adjacent fins to define an annular series of upright heat absorbin conduits for the fiow of a heat exchange medium, and means for delivering such a medium to the lower ends of the conduit.

16. A boiler comprising substantially concentric upright walls spaced apart through the major portions of their length and hermetically sealed at their upper and lower edges to provide an annular interior space for a body of liquid to be vaporized, a body of insulating material surrounding the outer surface of the outer wall, a plurality of substantially upright fins projecting from the exterior surface of the inner wall and all including laterally turned portions spaced from the last-mentioned wall and cooperating with the next adjacent fins to define an annular series of upright heat absorbing conduits for the fiow of a heat exchange medium, means for delivering such a medium to the lower ends of the conduit, and battle means preventing the fiow of the medium to the central space defined by the annular series of conduits.

17. An hermetically sealed boiler-condenser mechanism comprisin a boiler having spaced parallel upright walls sealed at their upper and lower edges and providing an annular interior space, insulating material covering the exterior surface of one of said walls, means for delivering a heating medium in heat exchange relation to the exterior surface of the other of said walls, an hermetically sealed condenser comprising upper and lower headers and condenser tubes interconnecting the same, a riser, connections between the riser and the boiler interior above and below the water line, and connections between the riser and the upper and lower headers, the lower header connection being spaced between the upper and lower boiler connections.

18. A boiler condenser assembly comprising substantially parallel walls defining an annular boiler space, an outlet conduit above the normal boiler water level, an inlet conduit therebelow, a condenser having upper and lower vapor and condensate connections, a single riser communicating with both of said conduits and with the upper and lower condenser connections, said lower condenser connection communicating with the riser intermediate the upper and lower con- REFERENCES CITED its, whereby ndensate may return to the The following references are of record in the lower conduit from the condenser and liquid disfil of this patent: charged with vapor through said outlet conduit 5 may separate therefrom and return directly to UNITED STATES PATENTS the boiler through lower conduit. and means be- Number Name v Date low the boiler for delivering a heat exchange ,44 44 Spaleck Feb. 13, 1923' medium thereto. ,64 ,284 Mitchell Aug. 23, 1927\ GLEN W. MILLER. 10 2,131,901 Parkton Oct. 4, 1938 EDWARD LUCAS KELLS. 2,419,234 Holihan Apr. 22, 1947" 

